Cao Yongkang from Shanghai Jiaotong University first visited an old street in Gyalze county of the Tibet autonomous region in 2013, he was thrilled.

"I was excited because there are still so many people living in the area, which helps keep the old street's authenticity alive," recalls Cao, an architecture professor.

The old street, located in the north of the county in Shigatse city, is at an elevation of about 4,000 meters.

It is a residential area with a history of more than 600 years.

The Palcho Monastery is located near the street.

Gyalze is today an important transport hub for Lhasa, Shigatse and another county called Yadong. But the old street in Gyalze was the center of business in the olden days when Tibetan merchants bought and sold goods from Indian and Nepalese traders.

The street still has one of Tibet's earliest coffee shops.

Cao was invited to help with the preservation of the ancient street in 2013 after some Shanghai local government officials went to work in Shigatse and noticed it.

"Gyalze is important in many ways. Earlier, the county was the only route to pass for people traveling from Nepal to Lhasa, through Yadong, and it has developed commercially as well. Gyalze also has good agriculture," Cao says.

In recent years, Gyalze's local government has been working to find ways to protect the old street's heritage from being drowned in commercial real estate activity.

The street is now home to about 100 local households. Walking down the street, visitors can find cows, sheep and dogs lying right in front of people's houses, as most local families rely on animal husbandry for a living.

Tashi Thondup, deputy director of the tourism bureau of Gyalze, says since 2013, the county government has worked with Cao's team from Shanghai to protect the old street's heritage.

By visiting the street twice each year, Cao and his team have made an evaluation, based on which only 13 old houses will be refurbished in the future. The other houses will remain untouched.

Cao urged Tashi Thondup and the other local officials to ask people to continue living in the street so that its heritage is preserved.

"One common problem (with urbanization) is that old streets are easily turned into commercial areas, with houses becoming shops and restaurants, and people no longer living in such places," Cao says, adding that when such areas develop, people tend to move out to modern houses.

"The best way to maintain an old house is to have people actually living in it. It is also the best way to preserve a street with heritage," he says.

Tashi Thondup says the county government is now rebuilding a street parallel to the old street that can be commercially developed instead of disturbing life in the old street of Gyalze.

Guge Kingdom, which founded around the 9th century but disappeared mysteriously during the 17th century, attracted many tourists every year with its heritage of color painting, clay figurines and sculptures.